1. Field of the Invention
The present invention relates to an implantable woven prosthesis and a method for manufacturing same. In an exemplary embodiment, the prosthesis is a tubular graft varying in diameter along its length. The prosthesis may be used, for example, by vascular or cardiovascular surgeons, for repairing portions of the cardiovascular system, including but not limited to all or portions of the ascending aorta, and aortic root. In an exemplary embodiment, the present invention may also applicable to valve sparing and Bentall-type procedures.
2. Description of Related Art
Tubular woven fabrics have been used for soft-tissue implantable prostheses to replace or repair damaged or diseased lumens in the body. Within the field of cardiothoracic surgery, for example, endoprostheses are used in the vascular system to prevent blood flow and pressure from rupturing a weakened or otherwise damaged section of the vessel. Such endoluminal conduits may be affixed in a specified location in the vessel by means of stents, hooks, sutures, or other mechanisms serving to secure the devices in place. Endoluminal tubular devices or conduits can also be used in other lumens in the body, such as in the esophagus and colon areas.
One area of specialty, replacement or repair of the aortic valve and/or the ascending aorta, in particular the sinuses of Valsalva, involves specialized and time consuming surgical procedures. These procedures have traditionally been performed with straight woven grafts. Although the procedures can be executed with a straight graft prosthesis, there is an increasing perception within the surgical community that vascular grafts incorporating bulges or bulbous portions to mimic the natural shape and profile of the human vasculature may be beneficial. Attempts to fabricate such grafts by others typically have caused problems in one or both of the areas of fabrication, surgical utility, and/or post-operative patency.
For example, some fabrication attempts have involved post-weaving processing such as stitching, suturing, or the seaming of cut sections of corrugated fabrics together in a manner that results in a graft comprising a corrugated expandable middle section. Such a graft requires additional and costly manufacturing steps. Furthermore, the resulting graft can compromise surgical utility and ease of use for the surgeon, since a sufficiently flat and smooth surface is not provided for anastomosis to occur on a bulbous portion. Such deficiencies complicate anastomosis procedures.
Additionally, the “seams” or “junctions” where the multiple components are brought together create localized portions of graft rigidity, strength, and change in porosity not found in other portions of the graft. The resulting non-uniform nature of the underlying graft forces the surgeon to consider orientation of the graft prior to and during implantation and/or anastomosis. This extra precaution required of the surgeon may distract him or her from other aspects of the surgery.
Furthermore, in vivo arterial pressure applied to grafts with corrugated bulbous sections may result in expanded shapes and dimensions that are drastically different when compared to the unpressurized state of such prosthesis commonly occurring during surgery. With such prostheses, the surgeon will therefore not be able to predict the in vivo performance of the prosthesis in terms of the clearance or engagement of valve leaflets with the inner sidewall of the prosthesis. Therefore, the surgeon may not fully appreciate how such a graft will function in vivo, and may not have any predictions as to long-term surgical success of the prosthetic thereby potentially jeopardizing the intended efficacy of the surgical procedure.
Other examples of fabricating prostheses for addressing problems relating to the ascending aorta and sinuses of Valsalva attempt to utilize shrinking characteristics of yarns in a controlled manner such that smaller diameter portions of a graft are created through the shrinking of weft yarns. While tapers may be able to be formed through such a procedure, concerns relating to suture retention strength as well as non-uniform porosity and yarn spacing of the fabric structure can cause problems for surgeons and/or long term durability of the prosthesis, when used for repairing portions of the ascending aorta. Additionally, the fabricator of such prostheses will be limited through the shrink coefficients of the yarns to design geometries of sufficient taper required for mimicking the sinuses of Valsalva.